This invention relates to a detector of the location of peak combustion pressure (LPP) in the combustion chamber of an internal combustion engine. Such a detector is useful in LPP ignition timing control systems, in which ignition timing is controlled so as to maintain peak combustion chamber pressure at a predetermined crankshaft rotational angle. Such systems are used in calibration of conventional ignition timing systems for internal combustion engines and have been suggested for closed loop control of such engines in motor vehicles.
An LPP ignition timing control requires a sensor capable of detecting the timing of peak combustion pressure. Sensors exist which have proven satisfactory in calibration work. An example is the engine headbolt sensor shown in the U.S. Pat. No. 4,491,010 to Brandt et al, issued Jan. 1, 1985. Other sensors have been incorporated with engine spark plugs in an effort to find an access point to the combustion chamber without retooling an engine block or head. However, there is always a search for a sensor using a different approach, which might show an improvement in cost, output signal, ease of assembly or installation, reliability or some other feature.